Novel Thermodynamic Model For Vapor-Liquid Equilibrium Of CO₂in Aqueous Solution Of 4-（Ethyl-Methyl-Amino）-2-Butanol With Designed Structures

Large-scale carbon dioxide emissions have caused the greenhouse effect,leading to global temperature rise and a large number of secondary disasters.At the same time,China has proposed a national strategic goal of reaching the carbon peak by 2030 and being carbon neutral by 2060.In this context,new and higher expectations are set for carbon dioxide capture technology.The post-combustion carbon dioxide capture technology of organic amines is considered to be one of the technologies with the highest technological maturity and the most promising rapid commercialization.The large energy consumption of regeneration in the process of carbon dioxide desorption is the main reason for the industrial application and promotion of amine capture of carbon dioxide.The development of high-efficiency carbon dioxide capture agents is one of the keys to reducing the energy consumption of desorption.Based on the analysis of the structure of tertiary amines and carbon dioxide capture performance reported in a large number of literatures,combined with the structure-activity relationship between the amine structure and the absorption and desorption performance explored in the previous work,tertiary amines only generate carbonates in the solution due to the CO₂ absorption.Therefore,it has lower desorption energy consumption than primary secondary amines,but its absorption rate is slower.For the amine-H₂O-CO₂ system,studying the thermodynamic model can not only obtain the concentration of each component in the system and the system pressure and temperature,but also greatly benefit the system mass transfer and process simulation.According to the structure-activity relationship between the amine structure and the CO₂ absorption and desorption performance,this paper designs and synthesizes a new structure-modified amine absorbent with higher absorption rate and lower desorption energy consumption—4-ethyl-methyl-amino-2-Butanol（EMAB）,and conduct experimental research on absorption performance and establishment of thermodynamic model.The main research contents are as follows:（1）The equilibrium CO₂ solubility,viscosity,dissociation constant and second-order reaction rate constant were measured,and the heat of absorption was calculated.The thermodynamic and kinetic properties of EMAB were analyzed and evaluated by comprehensive analysis methods,and were compared with several new tertiary amines（MPDL,DMAB and DEAB）and traditional commercial amines（MEA,DEA,MDEA,PZ and AMP）.Compare.The equilibrium solubility of 1-3mol/L EMAB aqueous solution to absorb carbon dioxide under the temperature range of 298.15-333.15 K and the partial pressure of carbon dioxide of 2.0-101.3 k Pa was measured by the gas-liquid equilibrium experiment,and the equilibrium carbon dioxide of the EMAB amine solution was found The solubility decreases with the increase of temperature,increases with the increase of carbon dioxide partial pressure,and decreases with the increase of amine concentration.The data of the pseudo first-order constant of carbon dioxide absorption in the temperature range of 0.1-0.4mol/L EMAB solution in the temperature range of 293.15-313.15K,that is,the first-order apparent reaction rate constant（k₀）,was measured by the stop-flow technique.It is close to 1,indicating that the basic catalytic mechanism can be used to explain the reaction between CO₂ and EMAB solution.The viscosity of 1-3 mol/L EMAB aqueous solution under the condition of 313.15 K with and without CO₂ was measured.The experimental results show that the viscosity of the EMAB aqueous solution increases with the increase of mole fraction and CO₂ loading.Using the method of titration to measure the acidity of the solution,the dissociation constant of the EMAB solution was measured at 293.15-318.15 K:p Ka=2318/T+2.12,and the results showed that p Ka decreased with the increase of temperature.Then,according to the Clausius-Clapeyron equation,the CO₂ absorption heat of EMAB is-46.3±1.1k J/mol.Studies have shown that EMAB has good CO₂ capture performance and is expected to become one of the most promising alternative amines in post-combustion CO₂capture technology.（2）In addition,this work also studied the gas-liquid equilibrium model of EMAB solution to absorb CO₂,and developed a new and improved C_f model based on the correction coefficient C_f model.This model is based on the correction of the hydrogen ion concentration in the EMAB-H₂O-CO₂ ternary system,and at the same time correlates the initial concentration of amine,the physical solubility of carbon dioxide and the carbon dioxide load.The AARD of the improved C_f model is 3.68%.Based on Debye-Hückel theory and Virie equation,introducing fugacity and activity coefficients,considering the effective partial pressure and effective concentration of the solution,a fugacity-activity model is proposed.The AARD of the fugacity-activity model is 2.3%.